I think a list of tags where the location wouldn't matter would be much shorter...
– littleadvOct 2 '14 at 6:05

Kinda seeing this as a separate feature now, since there are just so many. Matching tax* isn't hard, but there are so many one-off tags to match. What we might be able to do, and I have to look into it, is have a per-site configurable paragraph under the tag input field on the questions/ask page. This is the place to say "If your question goes beyond general fiscal advice that could equally apply to anyone regardless of location, you should consider indicating your location in your question if you'd like to receive a timely answer" or something to that effect. Lemme think on it a spell.
– Tim Post♦Oct 2 '14 at 8:02

A per-site configurable paragraph isn't a bad idea, but on the original idea, how about a simple moderator-configurable list of tags, so the burden of maintaining such a list isn't on Stack Exchange staff?
– Chris W. ReaOct 3 '14 at 19:12